linux-kernel - Re: [PATCH V4 2/4] dt-bindings: mmc: controller: Add max-sd-hs-frequency property

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Message-ID: <98bd97cd-0d34-4bb6-869f-68feec1de68e@kernel.org>
Date: Fri, 1 Aug 2025 11:00:39 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Sarthak Garg <quic_sartgarg@...cinc.com>,
 Ulf Hansson <ulf.hansson@...aro.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Adrian Hunter <adrian.hunter@...el.com>
Cc: linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 quic_cang@...cinc.com, quic_nguyenb@...cinc.com, quic_rampraka@...cinc.com,
 quic_pragalla@...cinc.com, quic_sayalil@...cinc.com,
 quic_nitirawa@...cinc.com, quic_bhaskarv@...cinc.com, kernel@....qualcomm.com
Subject: Re: [PATCH V4 2/4] dt-bindings: mmc: controller: Add
 max-sd-hs-frequency property

On 01/08/2025 10:45, Sarthak Garg wrote:
> Some platforms may require limiting the maximum frequency used in SD
> High-Speed (HS) mode due to board-level hardware constraints. For
> example, certain boards may include level shifters or other components
> that cannot reliably operate at the default 50 MHz HS frequency.
> 
> Introduce a new optional device tree property max-sd-hs-frequency to
> limit the maximum frequency (in Hz) used for SD cards operating in
> High-Speed (HS) mode.
> 
> Signed-off-by: Sarthak Garg <quic_sartgarg@...cinc.com>
> ---
>  .../devicetree/bindings/mmc/mmc-controller-common.yaml | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> index 9a7235439759..6c2529b976d1 100644
> --- a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> +++ b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> @@ -93,6 +93,16 @@ properties:
>      minimum: 400000
>      maximum: 384000000
>  
> +  max-sd-hs-frequency:

Use standard unit suffixes. s/frequency/hz/



> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      Maximum frequency (in Hz) to be used for SD cards operating in
> +      High-Speed (HS) mode. This is useful for board-specific limitations,
> +      such as level shifters or others where the card cannot reliably
> +      operate at the default 50 MHz HS frequency.

Don't repeat constraints in free form text.

default: